The proposed research will define number, properties, and pathogenic role of proteins associated with the outer membrane of H. influenzae. The results should add to current understanding of the epidemiology and pathogenicity of H. influenzae and human resistance to diseases caused by it. Optimal biochemical methods for the purification of the proteins of the outer membrane (OM) will be described. The OM proteins that are predominant and/or immunogenic in situ will be purified. Antibody to these OM proteins will be used to determine their distribution among isolates of non-encapsulated and encapsulated H. influenzae and other human bacteria. An attempt will be made to use these results to describe a new serologic typing system for H. influenzae and thereby probe further its epidemiology. The distribution of antibodies OM proteins will be studied in healthy individuals and in children recuperating from various H. influenzae diseases. The protective role of such antibodies will be studied directly in an infant rat model of H. influenzae b meningitis. Antigen defective mutants will be selected and tested in parallel with wild-type strains containing different OM proteins for pathogenicity in this experimental system. These results should define the pathogenic role of these antigens and the protective activity of antibody to them.